Ordinary Differential Equations Question Paper focuses on “Special Functions -2 (Beta)”.
1. β(m, n) = β(n, m). Is the statement true?
a) True
b) False
Answer: a
Explanation: L.H.S. = (beta(m, n) = frac{Gamma(m).Gamma(n)}{Gamma(m+n)}. )
R.H.S. ( = beta(n, m) = frac{Gamma(n).Gamma(m)}{Gamma(n+m)} = frac{Gamma(m).Gamma(n)}{Gamma(m+n)} = ) L.H.S.
Therefore, (beta(m, n) = beta(n, m).)
2. Which of the following function is not called the Euler’s integral of the first kind?
a) (beta(m, n) = int_0^1 x^{m-1} (1-x)^{n-1} dx (m>0, n>0) )
b) (beta(m, n) = int_0^{π/2} (sinθ)^{2m-1} (cosθ)^{2n-1} dθ )
c) (beta(m, n) = int_0^∞ frac{y^{n+1}}{(1+y)^{m+n}} dy )
d) (beta(m, n) = 2 int_0^{π/2} (sinθ)^{2m-1} (cosθ)^{2n-1} dθ )
Answer: b
Explanation: Euler’s integral of the first kind is nothing but Beta function. So, here only ( beta(m, n) = int_0^{π/2}(sinθ)^{2m-1} (cosθ)^{2n-1} dθ) is not the definition of Beta function.
3. Which of the following is not the definition of Beta function?
a) (beta(m, n) = 2int_0^1 x^{m-1} (1-x)^{n-1} dx (m>0, n>0) )
b) (beta(m, n) = 2int_0^{π/2}(sinθ)^{2m-1} (cosθ)^{2n-1} dθ )
c) (beta(m, n) = int_0^∞ frac{y^{n+1}}{(1+y)^{m+n}} dy )
d) (beta(m, n) = int_0^1 frac{x^{m-1}+x^{n-1}}{(1+x)^{m+n}} dx )
Answer: a
Explanation: (beta(m, n)) can be written as either (int_0^1 x^{m-1} (1-x)^{n-1} dx , (m>0, n>0))
(or)
(= 2 int_0^{π/2}(sinθ)^{2m-1} (cosθ)^{2n-1} dθ )
(or)
( = int_0^∞ frac{y^{n+1}}{left(1+yright)^{m+n}} dy ;or int_0^1 frac{x^{m-1}+x^{n-1}}{left(1+xright)^{m+n}} dx).
So the correct answer is (2int_0^1 x^{m-1} (1-x)^{n-1} dx (m>0, n>0) ) which is actually not the formula for Beta function.
4. What is the value of (beta(m, frac{1}{2}) )?
a) β(m, m)
b) 22m-1 β(m, m)
c) 22m+1 β(m, m)
d) 22m β(m, m)
Answer: b
Explanation: (beta(m, frac{1}{2}) = 2int_0^{π/2}(sinθ)^{2m-1} dθ )
(beta(m, m) = 2 int_0^{π/2}(sinθ)^{2m-1} (cosθ)^{2m-1} dθ )
( = 2^{-2m+2} int_0^{π/2}(2 sinθ cosθ)^{2m-1} dθ )
Substituting 2θ=φ,
( = 2^{-2m+1} int_0^π sinφdφ )
( = 2^{-2m+1}.2.int_0^{π/2}sinφdφ )
( = frac{1}{2^{2m-1}} beta(m, frac{1}{2}). )
5. What is the value of β(3,2)?
a) (frac{1}{14} )
b) (frac{1}{16} )
c) (frac{1}{12} )
d) (frac{1}{10} )
Answer: c
Explanation: (beta(3, 2) = frac{Gamma(3).Gamma(2)}{Gamma(3+2)} )
( = frac{2!1!}{4!} = frac{1}{12}.)
6. What is the value of (beta(frac{1}{4},frac{3}{4}))?
a) (pi )
b) (sqrt{2}pi )
c) (sqrt{2pi} )
d) ({2}pi )
Answer: b
Explanation: (beta(frac{1}{4}, frac{3}{4}) = frac{Gamma(frac{1}{4}).Gamma(frac{3}{4})}{Gamma(frac{1}{4}+frac{3}{4})} )
( = frac{pi}{sin frac{π}{4}} = sqrt{2}pi. )
7. What is the value of (int_0^{π/2}sqrt{sinθdθ} + int_0^{π/2}sqrt{cosθdθ} )?
a) (8sqrt{pi} frac{Gamma(frac{3}{4})}{Gamma(frac{1}{4})} )
b) (4sqrt{pi} frac{Gamma(frac{3}{4})}{Gamma(frac{1}{4})} )
c) (8sqrt{pi} frac{Gamma(frac{1}{4})}{Gamma(frac{3}{4})} )
d) (4sqrt{pi} frac{Gamma(frac{1}{4})}{Gamma(frac{3}{4})} )
Answer: a
Explanation: (int_0^{π/2}sqrt{sinθdθ} + int_0^{π/2}sqrt{cosθdθ} )
( = beta(frac{3}{4}, frac{1}{2}) + beta(frac{3}{4}, frac{1}{2}) )
( = 2 beta(frac{3}{4}, frac{1}{2}) )
( = 2frac{Gamma(frac{1}{2}).Gamma(frac{3}{4})}{Gamma(frac{1}{2}+frac{3}{4})} )
( = 2sqrt{pi} frac{Gamma(frac{3}{4})}{Gamma(frac{1}{4})} . frac{1}{(frac{1}{4})} )
( = 8sqrt{pi} frac{Gamma(frac{3}{4})}{Gamma(frac{1}{4})}. )
8. What is the value of (int_0^∞ frac{1}{(1+y)^5} dy )?
a) 1⁄2
b) 1⁄3
c) 1⁄4
d) 1⁄5
Answer: c
Explanation: (int_0^∞ frac{y^{1-1}}{(1+y)^5} dy )
n=1 and m + n = 5 which implies m=4.
(beta(4, 1) = frac{Gamma(4).Gamma(1)}{Gamma(4+1)} )
(frac{3!0!}{4!} = frac{1}{4} ).
9. What is the value of (int_0^1 frac{dx}{sqrt{1+x^4}})?
a) (beta(frac{1}{4}, frac{1}{2}) )
b) (frac{1}{4sqrt{2}}beta(frac{1}{4}, frac{1}{2}) )
c) (frac{1}{3sqrt{2}}beta(frac{1}{3}, frac{1}{2}) )
d) (frac{1}{4sqrt{3}}beta(frac{1}{4}, frac{1}{3}) )
Answer: b
Explanation: Substitute x2 = tanθ
Therefore θ varies from 0 to (frac{pi}{4}.)
(int_0^{π/4} frac{(secθ)^2}{2 secθ sqrt{tanθ}} dθ )
(= int_0^{π/4}frac{dθ}{2sqrt{sinθ cosθ}} )
(= frac{1}{4sqrt{2}} beta(frac{1}{4}, frac{1}{2}).)
10. What is the value of (int_0^1frac{(y^5+y^2)}{(1+y)^9} dy )?
a) (frac{1}{158} )
b) (frac{2}{167} )
c) (frac{1}{146} )
d) (frac{1}{168} )
Answer: d
Explanation: m-1 = 5 => m=6 and n-1 = 2 => n=3.
(beta(6, 3) = frac{Gamma(6).Gamma(3)}{Gamma(6+3)} )
(= frac{5!2!}{8!} = frac{1}{168}. )
11. Solve using the Beta function. (int_0^1 x^{-2} (1-x)^{-3} dx. )
a) Can be solved using a Beta function with m = -1 and n = -2
b) Can be solved using a Beta function with m = 1 and n = -2
c) Can be solved using a Beta function with m = -1 and n = 2
d) Can’t be solved using the Beta function
Answer: d
Explanation: This function can’t be solved using the Beta function as m and n have negative values. Beta function can’t be solved if m and n are negative numbers.
12. What is the value of (int_0^∞ (sech x)^5 dx )?
a) (frac{3pi}{80} )
b) (frac{3pi}{240} )
c) (frac{3pi}{16} )
d) (frac{pi}{240} )
Answer: c
Explanation: (int_0^∞ (sech x)^5 dx = frac{2^5}{4} beta(frac{5}{2}, frac{5}{2}) )
(displaystyle = frac{8 Gamma(frac{5}{2})Gamma(frac{5}{2})}{Gamma(5)} = frac{(8*frac{3}{2}*frac{1}{2}*sqrt{pi}*frac{3}{2}*frac{1}{2}*sqrt{pi})}{24} = frac{9π}{48}=frac{3π}{16}. )
13. What is the value of (beta(frac{9}{2},3) )?
a) (frac{16}{1287} )
b) (frac{16}{1278} )
c) (frac{14}{1287} )
d) (frac{16}{127} )
Answer: a
Explanation: (beta(frac{9}{2},3) = frac{Gamma(frac{9}{2})Gamma(3)}{Gamma(frac{9}{2}+3)} )
( = frac{Gamma(frac{9}{2})2}{frac{13}{2}*frac{11}{2}*frac{9}{2}*Gamma(frac{9}{2})} = frac{16}{1287}.)
14. What is the value of (int_0^1 x^5 (1-x)^6 dx)?
a) (frac{1}{12*11*10*9*8*7} )
b) (frac{1}{12*11*10*9*8} )
c) (frac{1}{12*11*10*9*8*7*6} )
d) (frac{1}{12*11*10*9*8*7*6*5} )
Answer: c
Explanation: Here, m-1 = 5 which implies m=6 and n-1 = 6 which implies n=7.
(beta(6,7)= frac{Gamma(6)Gamma(7)}{Gamma(13)} = frac{1}{12*11*10*9*8*7*6}. )
Global Education & Learning Series – Ordinary Differential Equations.
To practice all questions papers on Ordinary Differential Equations,